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Comment by danharaj | Hacker News Reader

> In addition, when you apply the Einsteinian theory to the entire universe, you can't explain the observable geometry of the universe.

https://en.wikipedia.org/wiki/Friedmann%E2%80%93Lema%C3%AEtr...

"The Friedmann–Lemaître–Robertson–Walker (FLRW) metric is an exact solution of Einstein's field equations of general relativity; it describes a homogeneous, isotropic expanding or contracting universe that is path connected, but not necessarily simply connected."

> No one has ever observed any dark matter

http://chandra.harvard.edu/press/06_releases/press_082106.ht...

"NASA finds direct proof of Dark Matter"

> or dark energy so far.

This is probably the only part of your post that actually came close to the truth. Dark energy is far more of a placeholder than dark matter at this point.

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1. I was referring to the fact that the observable matter of the universe is not enough to generate the nearly flat and accelerating universe.

2. I am quoting from the article.

"In addition to the Chandra observation, the Hubble Space Telescope, the European Southern Observatory's Very Large Telescope and the Magellan optical telescopes were used to determine the location of the mass in the clusters. This was done by measuring the effect of gravitational lensing, where gravity from the clusters distorts light from background galaxies as predicted by Einstein's theory of general relativity."

Since they are calculating the mass by using General Theory of Relativity (indirect measurement, you have to trust the theory for this), I don't see how this can be called direct detection.

3. We don't seem to disagree on this :)

https://en.wikipedia.org/wiki/Modified_Newtonian_dynamics#At...

'The most serious problem facing Milgrom's law is that it cannot completely eliminate the need for dark matter in all astrophysical systems: galaxy clusters show a residual mass discrepancy even when analysed using MOND.'

'Besides these observational issues, MOND and its generalisations are plagued by theoretical difficulties. Several ad-hoc and inelegant additions to general relativity are required to create a theory with a non-Newtonian non-relativistic limit, the plethora of different versions of the theory offer diverging predictions in simple physical situations and thus make it difficult to test the framework conclusively, and some formulations (most prominently those based on modified inertia) have long suffered from poor compatibility with cherished physical principles such as conservation laws.'

Basically, people have tried to fiddle with the laws as you suggested, but none of actually managed to fit the data better than GR + dark matter, plus the fiddling often just looked like curve-fitting without any good theoretical justification. Of course, the jury's still out.

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